DESCRIPTION

Adult -- Hornets, yellowjackets, and paper wasps are all
wasps which are 13 to 25 mm in length. Yellowjackets are small
yellow and black wasps which are sometimes loosely defined as
yellow and black hornets. The American species traditionally
known as hornets is primarily black with black and white
abdomens. The European hornet is a large yellow and brown wasp.
Paper wasps are characteristically long-legged, reddish or brown
to almost black insects with slender, spindle-shaped abdomens.

Egg -- Wasp eggs are small, white and sausage-shaped.

Larva -- Wasp larvae are legless white or cream grubs with
pale to dark brown heads. Larvae of most species are at least 14
mm long when fully grown.

Pupa -- Pupae are slightly shorter than mature larvae and
develop within silken cocoons in cells within the nest.

BIOLOGY

Distribution -- Hornets, yellowjackets, and paper wasps
occur throughout most temperate areas of the world.

Hosts -- These wasps prey on many types of insects,
particularly caterpillars, although hornets and yellowjackets are
also attracted to meat and sweet drinks.

Damage -- Because they prey on many harmful insects, these
wasps actually perform a beneficial function. However, when they
nest in lawns, yard trees and eaves of houses, wasps may
interfere with outdoor activities. Wasps are likely to sting
anyone who disturbs their nest. Paper wasps, however, tend to be
less aggressive than hornets and yellowjackets. Wasp stings are
painful and cause severe allergic reactions in some people.

Life History -- The nests of hornets, yellowjackets and
paper wasps are abandoned each year. In fall, virgin queens and
males leave the nests and mate. The males and workers eventually
die, but the queens overwinter in rock cracks, under bark, in
houses or underground. In spring, queens emerge and begin
building nests. Hornet nests are usually constructed above
ground in trees or shrubs; whereas those of yellowjackets are
usually constructed underground. The European hornet usually
constructs nests in hollow trees. Paper wasps make papery,
honeycomb-like nests usually located above ground in trees and
dense shrubbery, under eaves, or some sheltered area.

After constructing a small nest, the queen lays a single egg in
each cell of the comb. Two to 3 days later, the eggs hatch and
the queen begins to feed masticated insects to the larvae.
Within 12 to 18 days, the larvae mature. Fully grown larvae spin
silken caps over their cells and pupate. About 12 days later,
new adult workers emerge. These workers attend and feed larvae
that develop subsequently, enlarge nests, and under some
circumstances (e.g., death of queen), lay male eggs. After
raising the first brood of workers, the queen remains in the nest
and deposits eggs. Hornet and yellowjacket queens produce about
1500 eggs; paper wasp queens may lay several hundred during their
lifetime.

CONTROL

In spring or summer, control of wasps may be warranted.
Treatment should be done at night when the wasps are quiet. The
insecticide and method of treatment to use depends on the
location and type of nest.

Insecticides may be dusted or sprayed into the entrances of
hornet or yellowjacket nests whether above ground or below
ground. Openings of underground nests may be closed with a
shovel full of moist soil after treatment. Paper wasp nests are
easily treated since they are open and exposed.

Occasionally yellowjackets and hornets build nests inside the
walls of buildings. In such cases, the knothole or crack
entrance should be located and treated, but not plugged so that
returning wasps can carry the pesticide into the nest and
contaminate the whole colony. Most pesticides are effective
within 24 hours.